Folding-Generated Molecular Tubes Containing One-Dimensional Water Chains

A series
of indolo­carbazole–pyridine (IP) oligomers
were prepared that fold into helical conformations, and their folding
features in solution and in the solid state were revealed. Helical
folding of these IP foldamers is induced by dipolar interactions through
the ethynyl bond and π-stacking between two repeating units.
Upon helical folding, 1H NMR signals of aromatic protons
were significantly shifted upfield by Δδ = 0.5–2.2
ppm. In addition, hypochromic shifts and fluorescence quenching were
observed in the absorption and emission spectra. X-ray crystal structures
clearly demonstrated that IP foldamers folded to helical structures
with cylindrical internal cavities wherein 3 or 5 water molecules
were occupied by hydrogen-bonding interactions in a 1-D array, reminiscent
of transmembrane water channels, called aquaporins.

一系列的吲哚咔唑-吡啶（IP）寡聚物被合成，这些寡聚物能够折叠成螺旋构象，其溶液和固态状态下的折叠特性得到了揭示。这些IP折叠聚合物的螺旋折叠是通过两个重复单元之间的偶极相互作用以及乙烯基键和π-堆积作用诱导的。在螺旋折叠过程中，芳香族氢原子的1H NMR信号发生了显著的场向上移，位移量Δδ为0.5-2.2 ppm。此外，在吸收和发射光谱中观察到吸光度的降低和荧光猝灭。X射线晶体结构清晰地展示了IP折叠聚合物折叠成具有圆柱形内部空腔的螺旋结构，其中3个或5个水分子通过氢键相互作用填充在1D阵列中，这与跨膜水通道（称为水通道蛋白）的结构相似。